A flat type display apparatus such as a liquid crystal display device has become widespread due to its easiness in achievement of reduction in thickness. Such a display apparatus includes a display panel containing a large number of pixels. The display panel receives, from a drive circuit, signals for driving the pixels. This drive circuit is integrated, and is provided as a packaged arrangement such as a COF (Chip On Film). Such drive circuit is provided externally to the display panel. Alternatively, the drive circuit is directly mounted on a glass substrate of the display panel, as a COG (Chip On Glass) form. The signals for driving the pixels are provided to the drive circuit thus mounted on the glass substrate via wiring mounted on an FPC (Flexible Printed Circuit) connected to the display panel.
In order to ensure reliability of signal communication to the display panel, it is required for the COF and the FPC to be securely connected to the display panel. As a technique for improving reliability of such a connection, a technique for structurally reinforcing the FPC is disclosed in Japanese Unexamined Patent Publication No. 183247/1993 (Tokukaihei 5-183247; published on Jul. 23, 1993), for example. In this technique, the FPC is reinforced at both outer side end sections which receive stress, by providing a reinforcement member that has no electrical connection.
Verification of the reliability of the connection is also carried out by a test conducted after the COF or the FPC is connected to the display panel. A mainstream of such a test is an impression test carried out at a connecting part. The impression test examines, through an image, a state of a thermally compressed impression part, by an automated machine incorporating a microscope. More specifically, a state of the impression part such as a depth and a width are analyzed by use of a photographed image.
The flat type display apparatus are becoming used as a display section for various machines, due to its advantage that the display apparatus can be arranged so as to be thin in thickness. For example, use of the flat type display apparatus in machines such as an onboard display apparatus and a display apparatus of a controlling apparatus have been promoted. In such fields of use, the machines which include the flat type display apparatus are often placed under a harsh environment. In a case of a passenger car, the display apparatus is subject to vibration, high and low temperatures, and the like. The controlling apparatus that is used in factories and the like are also often placed in a similar environment as with the passenger car.
Use of the flat type display apparatus under such a harsh environment causes film base material used in the COF and FPC to receive stress. Therefore, as compared to a case where the flat type display apparatus is used under a normal usage environment, there is a high possibility that the film base material (particularly at a connecting part with the display panel) is to break.
As described above, structural reinforcement of the FPC can reduce the occurrence of breakage of the FPC that is caused by stress. However, it can also be fully considered that, under the harsh usage environment, the reinforcement may still not prevent damage to the FPC given due to stress that has been received for a long term. As a result, in a case where the FPC actually breaks, there is a possibility that the display panel cannot be able to carry out a display due to a disconnection thus occurred to the FPC. Such a situation hinders operation of the passenger car and the controlling apparatus.
Moreover, although the impression test can verify the reliability of the connection during a manufacturing step of the display apparatus, verification cannot be made once the display apparatus is marketed as a product. Therefore, even if the COF and the FPC are close to breakage as a result of continuous use of the display apparatus under the foregoing harsh environment, this state cannot be verified. Consequently, further continuous use of the display apparatus in such state results in breakage of the COF and the FPC. As a result, display can no longer be carried out by the display panel.